(1) Field of the Invention
The present invention relates to a process for etching metal and alloy surfaces and to the products of such process.
(2) Description of Related Art
Photochemical machining (PCM) and mechanical etching (e.g. drilling, stamping, cutting and related processes) are known processes for etching metal and alloy surfaces. Etching may be restricted to the surface as is often the case for artistic articles and jewelry or it may involve total penetration as is often the case for industrial articles. The metal/alloy may be in the form of a sheet, foil or an article and when in the form of a thin sheet or foil, the metal/alloy may be physically supported by a non-etchable substrate which may be optionally removed in the final etched product.
Traditional PCM is a complex process involving the prior preparation of a photo-tool. Firstly, a metal or alloy surface is coated with a polymerisable etch-resist layer. A photo-tool is prepared which is a negative of the required etch image and is often a silver photographic emulsion plate. The photo-tool is placed directly over the etch-resist layer and is then exposed to UV light. This causes the etch-resist layer to polymerize and harden in those areas exposed to the UV light to produce a latent negative image of the required etch in the etch-resist layer. The etch-resist layer is then chemically treated to remove the unexposed and unpolymerised area of the etch-resist. This is known as the development step. This chemical treatment is typically mildly alkaline when the etch-resist layer contains free acid groups.
The exposed areas of metal or alloy which are not protected by the polymerised etch-resist layer are then selectively removed by chemical etching from those areas protected by the etch-resist layer. Finally, the polymerised etch-resist layer is optionally removed. This is typically achieved by treatment with alkaline media using, for example, aqueous alkali.
Although PCM is widely used in the manufacture of etched metals and alloys it is tedious, expensive and wasteful of materials because the etch-resist layer is made separately and applied over the total area of the metal or alloy substrate. Furthermore, the photo-tool containing the negative image of the desired etch pattern is often distanced from the etch-resist layer and diffraction of the UV light irradiation can lead to development and polymerisation in unwanted areas of the etch-resist directly beneath the photo-tool masked areas. This needs to be taken into consideration when preparing the photo-tool and can reduce the density and definition of etched features of finer detail.
EP 746 638 discloses the use of solvent-based and hot melt ink jet inks to manufacture textured rollers. However, EP 746 638 does not disclose the composition of such inks.